The present invention relates to methods and apparatus for manufacturing for slide fasteners coiled filaments which have the interlocking teeth of the slide fastener.
Thus, the present invention relates to a method for manufacturing elongated coiled slide fastener filaments which are continuous and preferably made of a plastic material. The invention relates to that type of method wherein the coiled filament is formed on a setting gear wheel the teeth of which are utilized, as well as the gaps between these teeth, in the formation of the coil which may have the configuration of a flattened spiral or another configuration which will have an equivalent effect. The flattened spiral which forms the coiled filament has sharp kinks or bends where the interlocking teeth of the slide member are situated. Of course, the invention also relates to an apparatus for performing the method of the invention.
At the present time there are a number of different known methods and apparatus for manufacturing slide fasteners of the above general type. In general, the known methods and apparatus utilize a principle according to which the filament is wound in a number of different ways and by various different structures around consecutive teeth of a setting gear wheel, although it is also known to utilize a filament which is preliminarily bent into a spiral or zig-zag configuration separately from the gear wheel. In this latter event, the preliminarily shaped blank filament is fed onto the setting gear wheel to be heat treated so as to relieve the stresses in the row of convolutions of the coiled filament. There are also known methods and apparatus according to which initially depressions are impressed, as by hacking, into the filament, these depressions being provided periodically at equal intervals along the filament, and the filament blank which is obtained in this way is then fed in an enforced manner onto the setting gear wheel so that as the filament is bent the initially formed depressions provide the consecutive locking teeth situated along the respective coils of the filament.
It is because of drawbacks which are present in the above methods and procedures that the present invention has been provided.
With respect to the present state of the art, reference may be made to Finnish Pat. No. 36,574, Swedish Pat. No. 187,831, Danish Pat. No. 123,684 and the German Offenlegungschrift No. 2,150,350.
According to the above Finish Pat. No. 36,574, a slide-fastener manufacturing method is disclosed wherein the continuous filament is first given a planar zig-zag configuration with the locking teeth being provided at the sharp bends of this filament. The blank which is thus achieved is then fed onto the setting gear wheel in an enfored manner. The primary drawback of this type of method resides in the difficulties which are encountered during transport of the filament blank and during the feeding thereof onto the setting gear wheel, as well as difficulties encountered with respect to providing a bend in the filament at the proper point for forming a loop blank.
With respect to Swedish Pat. No. 187,831, there is disclosed a method and apparatus wherein a setting wheel is also employed, with a filament feeder moving in the axial direction of the wheel. In a direction which is transverse to the direction of movement of the filament feeder there is a gripping pin which moves in such a way that the filament is wound around an end of this gripping pin during movement of the filament feeder. This filament feeder carries a stop which at the extreme end of the range of movement of the filament feeder pushes the filament loop and circling the end of the gripping pin and shapes it into a locking tooth. The drawback of this method and apparatus resides in the complex paths of movement of the filament feeder and above all of the gripping pin, as well as in the difficulties encountered in providing the required synchronization of the movements of the different components.
With respect to Danish Pat. No. 123,684, referred to above, there is disclosed an apparatus intended to manufacture a slide fastener and having a first pair of rolls used to impress into the filament preliminary rudimentary curves and locking teeth. This same pair of rolls feed, in an enforced manner, the resulting filament onto the setting wheel which carries at its circumference a set of consecutive pins with the filament being fed into the spaces between these pins by way of a special piston which is arranged to reciprocate radially with respect to the setting wheel. The drawbacks with respect to this method and procedure are primarily the same as those referred to above in connection with Finnish Pat. No. 36,574.
There is also a publicly available Finnish patent application No. 3247/67, corresponding to Swedish announcement publication No. 324,075, wherein there is disclosed a slide-fastener manufacturing apparatus according to which the filament is wound so as to be contiguous with teeth of the gear setting wheel, utilizing a particular feeding means while at the same time a depression which produces the locking tooth is impressed into the filament. This apparatus has a stop which is fixed to the gear setting wheel and has its working face situated in a plane which is substantially flush with the innermost parts of the gaps between the teeth of the gear setting wheel. Adjacent to this setting wheel is a special filament guide which has a filament feeding channel through which the plastic filament passes. The filament guide has a substantially U-shaped punch projection which performs the initial pressing of the locking teeth against a stop when the filament guide is moved inwardly, radially toward the axis of the gear setting wheel. At the same time, the outer margin of the filament guide pushes the preceding filament section into a tooth gap of the gear setting wheel, whereupon the filament guide withdraws radially and subsequently moves axially, so that the filament sections are positioned side-by-side in a tooth gap. The drawback of this type of apparatus resides in the complexity of the moving parts and in the complexity of the paths of movement, as well as difficulties encountered in synchronization of the various moving components, these latter difficulties resulting in possible damage of the components.
The above method and apparatus greatly resemble the method and apparatus disclosed in German Offenlegungschrift No. 2,150,350. The only substantial difference resides in the fact that the method and apparatus disclosed in the German publication required a particular piston which in its outward movement, radially to the setting wheel, impresses the rudimentary locking teeth to the filament while the filament guiding channel acts as a countermember in this connection. With respect to the drawbacks of this apparatus, the above points with respect to the proceding disclosure also apply.